This is Eduardo from Honduras, i´m actually developing this project for my sister's science fair, and I would like to ask which changes, or what components we have to aggregate using a 12 V pump instead of a 5 V.
If you are using a 12V pump then you will need an external 12V power supply and you will not be able to power the pump directly from the Arduino's 5V pin. There are several videos on our How to Use an Arduino page that will be helpful: